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How to 'trick' PV into staying on during a grid outage

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  • #16
    Originally posted by SunEagle View Post
    While the SMA GTI has the ability to utilize up to 1500 watts of your pv array if the grid goes down the bad news is that without continuous sunshine even that power supply will fluctuate. That is why utilizing a battery system or generator is the only way to provide your loads a stable output.
    I already have a decent sized UPS for my home that powers my home office at full power for about 3 hours, more if I'm conservative. My thought was rather than an overly complex design with MB cutoffs and rewire the house at great cost, instead plug the SMA into the UPS which would then buffer the output, protecting electronics and providing stable power for my office needs versus trying to power the whole house which is unnecessary.

    For winter storm outages and/or night usage where PV output will be zero to little, switch back to the generator and let it do its thing.

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    • #17
      Originally posted by Burningislove View Post
      I already have a decent sized UPS for my home that powers my home office at full power for about 3 hours, more if I'm conservative. My thought was rather than an overly complex design with MB cutoffs and rewire the house at great cost, instead plug the SMA into the UPS which would then buffer the output, protecting electronics and providing stable power for my office needs versus trying to power the whole house which is unnecessary.

      For winter storm outages and/or night usage where PV output will be zero to little, switch back to the generator and let it do its thing.
      You're confused what the SMA SunnyBoy is. It is a grid tie inverter, just like you already have. You would need to replace your brand new inverter with the SMA SunnyBoy. When the grid is out, if it is sunny, you are able to throw a switch that allows one outlet to receive up to 1500W of AC directly from the solar panels. If the sun is down, no power. So yes, you could plug your existing UPS into that outlet, and the sun could charge your UPS to extend its use.

      What brand inverter do you have now?
      Solar Queen
      altE Store

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      • #18
        Originally posted by Amy@altE View Post
        You're confused what the SMA SunnyBoy is. It is a grid tie inverter, just like you already have. You would need to replace your brand new inverter with the SMA SunnyBoy. When the grid is out, if it is sunny, you are able to throw a switch that allows one outlet to receive up to 1500W of AC directly from the solar panels. If the sun is down, no power. So yes, you could plug your existing UPS into that outlet, and the sun could charge your UPS to extend its use.

        What brand inverter do you have now?
        Yes, I'm aware that my existing GTI (SolarEdge) would be replaced if/when I go forward. Since my SE is new, I'll likely wait until it's at EOL to replace it with something else (e.g. SMA), which is of course many years in the future I suspect (hope!). MA also has a rapid-shutdown requirement to meet legal code that must be considered. Many GTIs, including the one that my installer typically favors (favored), did not comply with this requirement and hence they switched to SE because it was one of the few that complies with code.

        I'd suspect the above MA code won't be an issue for many GTIs that don't currently comply, as I have many years before my SE fails and I'm sure many technologies will evolve during that time.

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        • #19
          SolarEdge is a fabulous product, expect a very long life from it. But if/when you do replace it, it's not as simple as switching it with a SMA. SolarEdge has the DC optimizers on the back of each panel, which is why it support rapid shutdown. They won't work without the inverter, so you'd have to remove all of them too. Much bigger project. DC coupling wouldn't work for you either for the same reason, the DC Optimizers need to talk to the inverter. Pretty much the only solution you'd have is to add AC Coupling, which is a bigger project as well.

          For the record, any grid tie inverter can comply with NEC 2014 Rapid Shutdown by using a disconnecting combiner box on the roof with a remote switch, like Midnite Solar's Disco Combiner and Birdhouse.
          Solar Queen
          altE Store

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          • #20
            Originally posted by Burningislove View Post
            Yes, I'm aware that my existing GTI (SolarEdge) would be replaced if/when I go forward. Since my SE is new, I'll likely wait until it's at EOL to replace it with something else (e.g. SMA), which is of course many years in the future I suspect (hope!). MA also has a rapid-shutdown requirement to meet legal code that must be considered. Many GTIs, including the one that my installer typically favors (favored), did not comply with this requirement and hence they switched to SE because it was one of the few that complies with code.

            I'd suspect the above MA code won't be an issue for many GTIs that don't currently comply, as I have many years before my SE fails and I'm sure many technologies will evolve during that time.
            your best bet is to wait for SolarEdge to announce the pricing on their upgrade of the inverter disconnect to support batteries and upgrade your solaredge inverter, wire up the office to the backup AC circuit and done.

            http://www.solaredge.us/files/pdfs/p...tasheet_na.pdf
            OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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            • #21
              Originally posted by ButchDeal View Post
              your best bet is to wait for SolarEdge to announce the pricing on their upgrade of the inverter disconnect to support batteries and upgrade your solaredge inverter, wire up the office to the backup AC circuit and done.

              http://www.solaredge.us/files/pdfs/p...tasheet_na.pdf
              Good idea. They are saying it will just be a firmware update to support the Tesla PowerWall 350V battery. I forgot about that.
              Solar Queen
              altE Store

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              • #22
                Originally posted by Amy@altE View Post
                Good idea. They are saying it will just be a firmware update to support the Tesla PowerWall 350V battery. I forgot about that.
                I think there is going to be some type of auto-transformer required for the PowerWall system.

                Comment


                • #23
                  Originally posted by SunEagle View Post
                  I think there is going to be some type of auto-transformer required for the PowerWall system.
                  you will have to replace the lower disconnect section below the inverter. For backup you will need an auto-transformer yes, and some re-wiring to get a backup breaker panel, and of course a battery of some kind.
                  OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

                  Comment


                  • #24
                    No updates since 2015 but I think it will benefit the discussion. This new IQ8 micro-inverter from Enphase is probably the solution to all of the issues mention in this forum. Supposedly this new hardware will allow solar power to run a house without a power grid or batteries. We have to wait until 2019.

                    http://www.acsolarwarehouse.com/news...hout-the-grid/



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                    • #25
                      Interesting, But without additional storage to buffer the supply (clouds, etc.) and loads (refrigerator cycling on and off, etc.) this seems like a recipe for damaged equipment due to power transients. It might work in an off grid type application (without storage) for small pre-planned loads like lighting etc. which are more tolerant to unexpected outages. Presumably a smaller portable UPS could be fed by the IQ8 as well to act as a buffer.

                      But, I'm under the impression the Tesla AC powerwall can do this already today using a wide variety of existing inverters. Presumably other available/soon to be available AC battery systems (LG, Panasonic, Mercedes) could as well? Does anyone actually have one of these with an existing Enphase, SolarEdge, or string solution? Does it really work? Realistically, what's the total cost:
                      A) <$5K
                      B) $5K to $10K
                      C) $10K to $15K
                      D $>15K?

                      When I spit balled the two or three Tesla powerwalls I would need to cover my consumption and the necessary electrical work to install, I was looking at well over $15K. A very nice stationary generator can be had for the same price or less in many cases if natural gas or propane are available,

                      But I agree. There should be one central device which serves as both switch gear and storage into which multiple inputs can flow in (grid, solar, generator) and out (loads). That's what we do with commercial UPS systems that have multiple MAINS inputs (for grid and generator -- solar not so much).

                      It seems Panasonic and LG (in Japan and Korea) are already thinking along these lines. But their residential consumption needs are much less than in the US.

                      -Jonathan

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                      • #26
                        What if you use a Separate battery and a small inverter to use as a substitute for the mains supply

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                        • #27
                          Originally posted by Kegonlegs View Post
                          What if you use a Separate battery and a small inverter to use as a substitute for the mains supply

                          it will be smoked in 3.5 minutes. 3 minutes to "qualify" the "Grid" and a couple more seconds to have the household 3Kw of PV backfeed the 500W inverter and boil the battery.
                          Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                          || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                          || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                          solar: http://tinyurl.com/LMR-Solar
                          gen: http://tinyurl.com/LMR-Lister

                          Comment


                          • #28
                            Originally posted by carsantini View Post
                            No updates since 2015 but I think it will benefit the discussion. This new IQ8 micro-inverter from Enphase is probably the solution to all of the issues mention in this forum. Supposedly this new hardware will allow solar power to run a house without a power grid or batteries.
                            Let's look at their claim.

                            "So, to address this limitation we have invented a microinverter technology that is completely grid agnostic. This means that even if the grid fails and there is sufficient sunlight, the Enphase system will continue to produce energy and meet the demands of the home or business."

                            Nope. A grid tie inverter that does not care what the grid is doing will not meet UL1741. What he probably means is that the inverter has a way to power a SEPARATE output that is not connected to the grid, similar to what the SMA inverters do. For example, a system with a transfer switch at the grid connection point that selects either grid or essentials panel can work. This, of course, will need a lot of installation work that will include installing a subpanel.

                            They also note that it "can" be integrated with their AC battery, but I suspect that for any realistic system it will effectively be a requirement. Their 1.2kwhr battery isn't much (only 280 watts AC output max) but it will be able to supply a little starting surge for motor-based appliances and let you run a night light at night - and of course you can parallel them. At that point you have to compare that sort of system against a conventional battery based system.

                            Comment


                            • #29
                              Originally posted by Kegonlegs View Post
                              What if you use a Separate battery and a small inverter to use as a substitute for the mains supply
                              Best case? Grid tie inverter starts up, overvoltages the smaller inverter and shuts down immediately. If you are lucky the smaller inverter might survive.

                              If you want backup get a generator. (More reliable, cheaper.) If you want solar backup get an SMA inverter with the Secure Power feature. (Not that reliable but almost free.) If you want solar backup at night get an SMA inverter and a $69 UPS from Best Buy.

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                              • #30
                                Originally posted by Burningislove View Post
                                ...I'm totally fine with this being a manual process to turn on and then switch back to normal operations once the grid gets back online.
                                ... I'd much rather utilize the system I already have...
                                Don't try to trick it to be on. Waste of money & won't match load cycle (cloudy, night).
                                Why not buy or lease an electric car (EV, PHEV) which would be charged with your system? Connect a 12VDC inverter (car type, 1500W or RV camper type, 5000W) & run extension cords to appliances or use manual interlock to power house (same as with Generac). Plenty of deals on used cars too.
                                Drive car to charging station (Chargepoint) if needed. You can even find free stations. Back to house for a few hours or days of power.
                                Theoretically you could replace a gas car with electric & have net savings or short term breakeven.
                                Who wins a prize for a solution you choose? Interested to hear update...

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